When you arrive at Manila airport there is a single authorised airport Taxi office which has posted fixed rates to various destinations around Luzon. The price above was a guess, and we're not absolutely sure what route they would take. If it is to go up the North Luzon Expressway to Clark and then down the new freeway to Subic then that could take anything from 2.5 on a really good day to 4+ hours, depending particularly on how bad the traffic is in Manila (the airport is on the south side so you have to cross metro Manila).